Two vertical divs within a 100% height div

Question

Sorry for my bad english, hope you will understand my issue.

I'm turning my head around a problem that I know I've been solving once before. The issue is that I need two DIVs inside a div where one of the DIVs has a given height and the other one fills up the rest of the parent div height. The problem is that the second div (with no defined height, or 100% height) needs to be overflow-able with an vertical Scroller. All this is to make an "outlook" lookalike windowsetup where you operate a list on the left and an actionwindow on the right. The left list needs a header where you can limit the list as well as search.

Have a look at http://kokongcrm0.server111.wdc.webdeal.no/index-test.php to find an example of the issue.

All help is good help (!) Thanx in advance. I would be so glad if someone could help!